Effect of p-GaN layer grown with H2 carrier gas on wall-plug efficiency of high-power LEDs

Abstract

The effect of employing different carrier gases (H2 only and 1:1 vol% N2:H2) in the p-type GaN (p-GaN) layer on the wall-plug efficiency (WPE) of high-power light-emitting diodes (LEDs) is studied. Since GaN crystal could be a two-dimension (2-D) growth mode in H2 ambient, better quality and smoother surface of the p-GaN were obtained. The current spreading performance of the p-GaN layer using H2 alone as the carrier gas was enhanced, resulting in advanced light output power (LOP). In addition, turn-on voltage and dynamic resistance at 500mA, which can strongly contribute to the WPE, were also reduced by 0.12V and 0.13Ω, respectively. The studied device with H2 as the carrier gas in the p-GaN layer (p-H2 layer) exhibits 9.5% and 12.4% improvements in LOP and WPE at 500mA over the device (N2/H2=1:1), as well as significantly better electrostatic discharge robustness. Therefore, the use of a p-H2 layer can effectively improve the performance of GaN-based LEDs for high power applications.